In recent years, interest has risen in comfort and health, in particular with respect to applications of clothing and daily necessities. Also, fabrics are being asked to (a) have high functionality, such as an antibacterial action, odor preventing action, deodorizing action, shielding from ultraviolet light, heat storage, etc. and (b) have comfort-related functions such as moisture permeability, waterproofness, water repellency, etc. for allowing sweat etc. to evaporate and the wearer to keep dry. As a method for realizing the functions of (a) above, use is generally made of the method for mixing in particles having the above functions with the yarn itself at the spinning stage (see Japanese Unexamined Patent Publication (Kokai) No. 2-182902) and the method of imparting the same by after-treatment methods such as impregnating or coating a fabric with a urethane or other resin in which particles have been added (see Japanese Unexamined Patent Publication (Kokai) No. 2-264074).
In the former method of mixing particles into the fibers, particles of a size on the submicron order enabling spinning are required. Even if addition is possible, the particles may lose their function due to the spinning conditions (particularly heat), the strength of the yarn may deteriorate or the spinning yield may fall, or it might not be possible to deal with small lots. For these and other reasons, it has been more convenient to impart the function by resin treatment and other after-treatment methods. In such after-treatment methods, however, there is the disadvantage that the resin constrains the fibers and therefore the feel of the fibrous substrate is remarkably impaired. Further, there was the problem that the resin itself would fall away during use or washing and the function would be lost.
On the other hand, a fabric having the functions of (b), that is, moisture permeability, waterproofness, and water repellency, is made much use of in sportswear applications such as for windbreakers. This fabric is generally obtained by coating a fabric with a urethane which foams at the time of solidification. In this case too, due to the entrance of the resin inside the fabric structure, there is the problem that the freedom of the fabric becomes remarkably lower and the feeling of the fiber becomes hard. The hardness of the feel cannot be avoided even with use of soft resins such as a urethane.
Therefore, to solve the above-mentioned problems, in the case of a moisture-permeable waterproof fabric coated with an elastic polymeric substance for use for a windbreaker etc., it has been considered to improve the feeling by controlling the permeation of the elastic polymeric substance into the fabric. As such a method, there are the method of applying hot calendering to the fabric to press the surface of the fabric and smooth it and the method of applying a fluorine compound or other repellent to the fabric in advance so as to prevent permeation (see Japanese Unexamined Patent Publication (Kokai) No. 58-144178).
In this method, however, since the fabric is smoothed by a hot calender, the fabric as a whole is given a paper-like hard feeling. Further, there is less permeation of the elastic polymeric substance, and therefore, the problems such as decrease in the peel strength of the film of the elastic polymeric substance. Even when treating the fabric by a repellent, since there is less permeation of the elastic polymeric substance in the same way, there is the problem of decrease in the peel strength of the film of the elastic polymeric substance.
Next, looking at an artificial leather composite material of a nonwoven fabric and an elastic polymeric substance (mainly urethane), coated artificial leather obtained by impregnating a nonwoven fabric with an elastic polymeric substance and forming on the surface of the impregnated substrate a covering layer of an elastic polymeric substance or a suede-like or nubuck-like product obtained by buffing the impregnated substrate to form a fiber pile layer are being used for shoe materials, coats and other garments, and furniture. In these applications, a feeling closer to that of natural leather is sought. Research is under way on a more flexible artificial leather. These studies are trying to obtain greater flexibility by inhibiting the bonding between the fibers and urethane.
For example, there are the following:
(i) An artificial leather obtained by impregnating an elastic polymeric substance into a nonwoven fabric, a paste polymeric substance with a different solvent from the impregnated elastic polymeric substance, covering the surface of the constituent fibers of the nonwoven fabric or filling part of the space created by the constituent fibers and solidifying the same, then removing the paste polymeric substance to form cavities between the fibers and elastic polymeric substance (for example, see Japanese Examined Patent Publication (Kokoku) No. 45-18745 and Japanese Unexamined Patent Publication (Kokai) No. 49-109697), PA1 (ii) An artificial leather obtained by treating a nonwoven fabric by a silicone resin, followed by impregnating the same with an elastic polymeric substance, whereby the bonding between the fibers and the elastic polymeric is prevented (see Japanese Examined Patent Publication (Kokoku) No. 45-33797), PA1 (iii) An artificial leather obtained by applying, to a nonwoven fabric, a pretreatment solution comprising mainly colloidal silica, causing migration of the colloidal silica at the time of drying to cause greater presence at the surfaces of the nonwoven fabric, impregnating and solidifying an elastic polymeric substance, then pulverizing and removing the colloidal silica by a mechanical method so as to change the amount of the elastic polymeric substance impregnated into the nonwoven fabric, in the direction of thickness of the nonwoven fabric (see Japanese Examined Patent Publication (Kokoku) No. 58-9191), PA1 (iv) An artificial leather obtained by the process of production of treating a nonwoven fabric with a surfactant to make the fiber surface hydrophilic, followed by impregnating a solution of a solvent based elastic polymeric substance to which a surfactant has been added, then causing the elastic polymeric substance to solidify in water so as to facilitate permeation of water at the interface of the fibers and the elastic polymeric substance and obstruct bonding of the fibers and elastic polymeric substance (see Japanese Examined Patent Publication (Kokoku) No. 61-42033), and PA1 (v) An artificial leather obtained by the process of impregnating a nonwoven fabric comprising islands-in-sea fibers with a solution of an elastic polymeric substance, then causing the elastic polymeric substance to solidify in water and suitably thereafter dissolving out the sea component of the islands-in-sea fibers by a solvent so as to create a substantially complete nonbonded state between the remaining island component fibers and the elastic polymeric substance (see Japanese Unexamined Patent Publication (Kokai) No. 64-85377). PA1 (a) a sufficient flexibility could not be obtained since the paste polymeric substance used for the pretreatment did not sufficiently coat the fibers as a whole. PA1 (b) the impregnability of the elastic polymeric substance became poor and a sufficient dynamic strength could not be exhibited, PA1 (c) the productivity fell, and PA1 (d) the increase in the cost of recovery for treating the waste liquor. PA1 (a) a nonwoven fabric treated with a silicone resin fell in strength and easily deformed in shape during the processing, making it susceptible to trouble in the cutting and other processes and PA1 (b) the mold releasability of the silicone was made sufficient use of, but there was insufficient prevention of bonding between the fibers and elastic polymeric substance and the flexibility was inferior. PA1 (a) the colloidal silica used for the pretreatment collected at the surface layer portions of the nonwoven fabric due to migration, and therefore, the fibers and elastic polymeric substance bonded at the center portion of the nonwoven fabric. Further, even at the surface layer portions, the ratio of bonding of the fibers and elastic polymeric substance was low, but the majority of the fibers were partially bonded and PA1 (b) there was a problem of the residue of the colloidal ilica and uneven dyeing. PA1 (a) the bonding was insufficiently prevented, numerous partial bonded structures were seen, and there was insufficient flexibility. PA1 (a) the leather was flexible, but small denier island components remained, and therefore, the wear resistance and other dynamic strength were inferior, PA1 (b) the fibers were limited to special fibers of the islands-in-sea type, and PA1 (c) it took time to dissolve out the sea component and there were problems environmentally speaking as well.
These known artificial leathers, however, have had the following problems:
That is, regarding the artificial leather of (i),
Further, when a large amount of the paste polymeric substance was used to try to obtain sufficient flexibility,
Regarding the artificial leather of (ii),
On the other hand, regarding the artificial leather of (iii),
Regarding the artificial leather of (iv),
Regarding the artificial leather of (v),
As explained above, at the present time, none of the artificial leathers simultaneously satisfies the contradictory properties of flexibility and high dynamic strength (in particular wear resistance).